Models/Customer.cs

using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace InsuranceProductManager.Models
{
    /// <summary>
    /// 生命保険業務用 顧客情報モデル
    /// </summary>
    public class Customer
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int CustomerId { get; set; }

        [Required(ErrorMessage = "氏名（漢字）は必須です。")]
        [MaxLength(100)]
        public string FullName { get; set; } = string.Empty;

        [MaxLength(100)]
        public string? FullNameKana { get; set; } // フリガナ（任意）

        [Required(ErrorMessage = "生年月日は必須です。")]
        [DataType(DataType.Date)]
        public DateTime BirthDate { get; set; }

        [Required(ErrorMessage = "性別は必須です。")]
        [MaxLength(10)]
        public string Gender { get; set; } = string.Empty; // "男性" "女性" "その他"

        [Required(ErrorMessage = "郵便番号は必須です。")]
        [RegularExpression(@"^\d{3}-\d{4}$", ErrorMessage = "郵便番号はXXX-XXXX形式で入力してください。")]
        public string PostalCode { get; set; } = string.Empty;

        [Required(ErrorMessage = "住所（都道府県・市区町村・番地）は必須です。")]
        [MaxLength(200)]
        public string Address { get; set; } = string.Empty;

        [Phone]
        [MaxLength(20)]
        public string? PhoneNumber { get; set; }

        [EmailAddress]
        public string? Email { get; set; }

        [MaxLength(100)]
        public string? Occupation { get; set; } // 職業

        [DataType(DataType.DateTime)]
        public DateTime CreatedAt { get; set; } = DateTime.Now;

        /// <summary>
        /// 年齢を算出
        /// </summary>
        public int GetAge()
        {
            var today = DateTime.Today;
            int age = today.Year - BirthDate.Year;
            if (BirthDate.Date > today.AddYears(-age)) age--;
            return age;
        }
    }
}

Views/LifeInsuranceMvc/AddCustomer.cshtml

@model InsuranceProductManager.Models.Customer

<h2>顧客登録（生命保険用）</h2>

<form asp-controller="LifeInsuranceMvc" asp-action="AddCustomer" method="post">
    <div>
        <label asp-for="FullName">氏名</label>
        <input asp-for="FullName" class="form-control" />
        <span asp-validation-for="FullName" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="FullNameKana">氏名（カナ）</label>
        <input asp-for="FullNameKana" class="form-control" />
        <span asp-validation-for="FullNameKana" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="BirthDate">生年月日</label>
        <input asp-for="BirthDate" type="date" class="form-control" />
        <span asp-validation-for="BirthDate" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="Gender">性別</label>
        <select asp-for="Gender" class="form-control">
            <option value="">選択してください</option>
            <option value="男性">男性</option>
            <option value="女性">女性</option>
            <option value="その他">その他</option>
        </select>
        <span asp-validation-for="Gender" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="PostalCode">郵便番号</label>
        <input asp-for="PostalCode" class="form-control" placeholder="例: 123-4567" />
        <span asp-validation-for="PostalCode" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="Address">住所</label>
        <input asp-for="Address" class="form-control" />
        <span asp-validation-for="Address" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="PhoneNumber">電話番号</label>
        <input asp-for="PhoneNumber" class="form-control" />
        <span asp-validation-for="PhoneNumber" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="Email">メールアドレス</label>
        <input asp-for="Email" class="form-control" />
        <span asp-validation-for="Email" class="text-danger"></span>
    </div>
    <div>
        <label asp-for="Occupation">職業</label>
        <input asp-for="Occupation" class="form-control" />
        <span asp-validation-for="Occupation" class="text-danger"></span>
    </div>

    <button type="submit" class="btn btn-primary mt-2">登録</button>
</form>

@section Scripts {
    <partial name="_ValidationScriptsPartial" />
}

Views/LifeInsuranceMvc/CustomerList.cshtml

@model IEnumerable<InsuranceProductManager.Models.Customer>

<h2>顧客一覧</h2>

@if (Model != null && Model.Any())
{
    <table border="1" cellpadding="5">
        <thead>
            <tr>
                <th>ID</th>
                <th>氏名</th>
                <th>フリガナ</th>
                <th>生年月日</th>
                <th>年齢</th>
                <th>性別</th>
                <th>郵便番号</th>
                <th>住所</th>
                <th>電話番号</th>
                <th>Email</th>
                <th>職業</th>
                <th>登録日</th>
            </tr>
        </thead>
        <tbody>
            @foreach (var customer in Model)
            {
                <tr>
                    <td>@customer.CustomerId</td>
                    <td>@customer.FullName</td>
                    <td>@customer.FullNameKana</td>
                    <td>@customer.BirthDate.ToString("yyyy-MM-dd")</td>
                    <td>@customer.GetAge()</td>
                    <td>@customer.Gender</td>
                    <td>@customer.PostalCode</td>
                    <td>@customer.Address</td>
                    <td>@customer.PhoneNumber</td>
                    <td>@customer.Email</td>
                    <td>@customer.Occupation</td>
                    <td>@customer.CreatedAt.ToString("yyyy-MM-dd HH:mm")</td>
                </tr>
            }
        </tbody>
    </table>
}
else
{
    <p>登録された顧客はまだいません。</p>
}

<p>
    <a asp-controller="LifeInsuranceMvc" asp-action="AddCustomer">新規顧客登録へ戻る</a>
</p>

実行時エラー

SQLite Error 1: 'table Customers has no column named Address'

つまり、
• 修正したCustomer モデルには Address プロパティがある
• でも SQLite の Customers テーブルには Address カラムが存在しない

ので、INSERT しようとしたときにコケています。

修正方法：DBを消して作り直す

rm InsuranceProductManager.db
dotnet ef migrations add Init
dotnet ef database update

UI